10 Sorting, Performance/Stress Tests

Exercise Set 10 c 2006 Felleisen, Proulx, et. al. 10 Sorting, Performance/Stress Tests In this problem set you will examine the properties of the different algorithms we have seen as well as see and design new ones. The goal is to learn to understand the tradeoffs between different ways of writing the same program, and to learn some techniques that can be used to explore the algorithm behavior. Etudes: Sorting Algorithms To practice working with the ArrayList start by implementing the selection sort. Because we will work with several different sorting algorithms, yet want all of them to look the same the selection sort will be a method in the class that extends the abstract class ASortAlgo. A sorting algorithms needs to be given the data to sort, the Comparator to use to determine the ordering, and needs to provide an access to the data it produces. Additionally, the ASort class also includes a field that represents the name of the implementing sorting algorithm. abstract class ASortAlgo<T> { /∗∗ the comparator that determines the ordering of the elements ∗/ public Comparator<T> comp; /∗∗ the name of this sorting algorithm ∗/ public String algoName; /∗∗ ∗ Initialize a data set to be sorted ∗ with the data generated by the traversal. ∗ @param the given traversal ∗/ abstract public void initData(Traversal<T> tr); /∗∗ ∗ Sort the data set with respect to the given Comparator ∗ and produce a traversal for the sorted data. ∗ @return the traversal for the sorted data ∗/ abstract public Traversal<T> sort(); } 1 c 2006 Felleisen, Proulx, et. al. Exercise Set 10 1. Design the class ArrSortSelection that implements a selection sort and extends the class ASortAlgo using an ArrayList as the dataset to sort. The ArrayList becomes an additional field in this class. • The initData initializes the ArrayList by adding to it all the data generated by the given Traversal. • the new method selectionSort implements a mutating selection sort on this ArrayList. There are numerous lecture notes and labs from the past several years available online that guide you through the design of selection sort. The third part of you draft textbook has a section on selection sort on pages 102-112. • The sort method invokes a selection sort on this ArrayList and returns an instance of ALT the Traversal over the data in an Ar- rayList. • Do this once you include the code in the main part of your assignment. Include in the class a self test in the form of a method testSort() that provides a test for all methods in this class. There is an example of this technique in the AListSortInsertion class provided with this homework. 2. Design the class ArrSortInsertion that implements a mutating insertion sort for an ArrayList and extends the class ASortAlgo in that same way as was done for the selection sort. You may work on this part with your partner if you wish — or get any help you need. However, you must make sure that at the end you understand every part of the code and how the tests were designed. Sorting out Sorting We have seen by now three different ways to sort a collection of data: The insertion sort, the quicksort, and the binary tree sort. The binary tree sort was hidden — we first designed the method to in- sert data into a binary search tree, then we designed the traversal over the binary search tree that generated the elements in the desired order. The algorithms all have the same purpose, yet they do not conform to the same interface. They also deal with the data structured in different ways. However, we would like to compare these algorithms for efficiency 2 Exercise Set 10 c 2006 Felleisen, Proulx, et. al. (speed). ASortAlgo class: Reporting the results Our first task is to design wrappers for all these algorithms that will al- lows us to use them interchangeably to sort any collection of data supplied through an iterator. Of course, we want all of them to produce the data in a uniform format as well. Therefore, we want all of these algorithms to produce a traversal for the sorted list. Because the traversal of a binary search tree involes quite a lot of com- putation, to make to comparisons fari, we will conclude the binary tree sort by producing an sorted ArrayList, generated by the data produced by the traversal of the binary search tree we have constructed. ASortAlgo class: Initializing the data The abstract class ASortAlgo introduced in the Etudes provides a uniform wrapper for all sorting algorithms. The initData method consumes the given traversal for the data to be sorted and saves the given data in a data structure appropriate for this algorithm. For the algorithms that are based on the ArrayList the initData method creates a new ArrayList and adds all elements generated by the given Traversal. For the AListSortInsertion class that implements the insertion sort for a recursively built AList, the initData method copied the given data into a new AList. For the quicksort algorithm that is based on recuesively build lists, this will not be necessary - as the algorithm traverses over the data and constructs two new lists - the upper and the lower partition, and does not use any properties of the lists. Finally, for the binary tree sort the task of constructing the binary tree comprises a substantial amount of work, and so should be done as a part of the sort method. Therefore, the initData method just copies the reference to the Traversal. We provide an example of a class that implements the insertion sort algorithm for data saved as AList<T>. ASortAlgo class: Running the timing tests To measure the time each algorithm takes to complete its task, we will invoke each algorithm in three parts. First, we provide the data to sort and invoke the initData method. Next we start the timer, invoke the sort method and stop the timer when the method returns the result. Finally, we check that the data was indeed sorted and record the result. We will test each of the several sorting algorithms on several datasets 3 c 2006 Felleisen, Proulx, et. al. Exercise Set 10 (varying the dataset size and whether the data is in the original order as received from the database, or is randomized). For each dataset we will use several different Comparators — by name and state, by latitude, and by zip code. The results will be recorded in a uniform way, so that we may then look for patterns of behavior. Here is a summary of the algorithms you will implement. Please, use the names given below: • ArrSortSelection — done as a Part 1 of the Etudes • ArrSortInsertion — done as Part 2 of the Etudes • AListSortInsertion — provided • ABinaryTreeSort — modify the solution to homework 5 • AListSortQuickSort — to be done (modify 8.1 part 9 of homework 8) • ArrSortQuickSort — to be done 10.1 Problem Design the method in the Tests class that determines whether the data generated by the given Traversal iterator is sorted, with regard to the given Comparator. Later, you will need the same method in the class TimerTests. 10.2 Problem Complete the design the classes AListSortSelection and AListSortInsertion. Include in each class a self test in the form of a method testSort(Tests tests) that provides a test for all methods in this class. 10.3 Problem Design the class ABinaryTreeSort that that extends the ASortAlgo class. It performs the binary tree sort on the data supplied by the Traversal iterator. The sort method first builds the binary search tree from the data provided by the iterator, then saves the data generated by the inorder traversal in an ArrayList or in an AListOfCities data structure. 4 Exercise Set 10 c 2006 Felleisen, Proulx, et. al. Include in each class a self test in the form of a method testSort(Tests tests) that provides a test for all methods in this class. 10.4 Problem Design the class AListSortQuickSort that performs the recursively defined quicksort on the data supplied by the Traversal iterator and producing an AListOfCities data structure. You will need a helper method to append two lists together. HtDP has a good explanation of quicksort. Include in each class a self test in the form of a method testSort(Tests tests) that provides a test for all methods in this class. 10.5 Problem Design the class ArrSortQuickSort that that extends the ASortAlgo class. It performs the quicksort sort on an ArrayList. The ArrayList is initialized from the data supplied by the Traversal iterator. You may use any textbook or the web to find an implementation of this algorithm, but you are responsible for the correctness of your implementation. Include in each class a self test in the form of a method testSort(Tests tests) that provides a test for all methods in this class. Note: If you are having problems with this algorithm, go on to the Time Trials and finish this only if you have time left. Part 2: Time Trials All of the tests we designed as the part of our code sorted only very small collections of data. It is important to make sure that the programs work well for large amounts of data as well. It is possible to estimate the amount of time an algorithm should take in comparison to others. However, we would like to verify these results on real data, and learn in the process what other issues we need to take into consideration (for example, the space the algorithm uses, and whether the data is already sorted or nearly sorted).

Load more